Manual PID Tuning - CH6 not altering P_Rate correctly

Hi. I’m following the ‘In Flight Tuning Guide’ and have hit a problem quite early on in the process. As instructed in the guide, I’ve done the following:

  • Set the CH6 Opt to “Rate Roll/Pitch kP”

  • Set Min to 0.08, Max to 0.20

  • Push the “Write Params” button

When I set the knob to either extreme, I get the correct min/max values returned in MP after a refresh. The problem I’m having is I can’t get anything but the min/max values. When I turn the knob I get the min value returned until I pass the mid point of the knob which then returns the max value. So when the knob is set between 0-50% I get a P_Rate of 0.08 and when set between 50-100% I get a P_Rate of 0.20. This is not just what I’m seeing in MP either. I get the same behaviour in actual testing. I get sluggish response with no change up to around 50% of the knob followed by uncontrollable oscillation above 50% (0.08 jumping up to 0.20). I apologise if this is something well documented elsewhere. I’m having trouble articulating my problem accurately.
Any help would be very much appreciated. I could achieve the tuning by manually altering the PID values in MP, ‘Write Params’ and test but that would take ages. Cheers

P.S.
I know auto-tune exists but I can’t afford to break anything if it goes wrong. I can handle human error causing damage but I don’t want an expensive self-destructed mess.

When you did your radio calibration, did you calibrate the channel you are using to set the values for Auto Tune using the VR (pot) knob? It sounds like your transmitter is outputting min and max values for the channel as if your VR knob is a SPST switch.

Common mistake would be calibrating that channel with a switch, and then later switching the transmitter configuration for that same channel to use a knob (pot) without re-calibrating.

If I remember correctly, I re-calibrated. CH6 is definitely displaying a full, smooth PWM range in the calibrate window. I’ll re-calibrate when I get home and report back.

Another thing you could check is to make sure you don’t have a mixer turned on that’s using Channel 6.